What was once called p22 from Drosophila was cloned in Fisher's lab and crystallized by Keefe for x-ray crystallography. The protein has since been renamed crp-1, for chromatin remodelling protein. Samples from the same preparation that was used to grow crystals were prepared for the STEM. Mass measurements indicate that the protein exists as a tetramer of approximately 70kD. The actual sequence molecular weight of the monomer is 17kD, not 22kD. This result should be helpful in interpreting the x-ray crystallographic results.